A communication system can be seen as a facility that enables communication sessions between two or more nodes such as fixed or mobile communication devices, access nodes such as base stations, servers and so on. A communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define the manner how communication devices shall communicate with the access nodes, how various aspects of the communications shall be implemented and how the devices shall be configured.
A communication can be carried on wired or wireless carriers. Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Wireless systems can be divided into coverage areas referred to as cells, such systems being often referred to as cellular systems. An example of cellular communication systems is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). This system is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. A further development of the LTE is often referred to as LTE-Advanced. The various development stages of the 3GPP LTE specifications are referred to as releases.
Radio services areas are typically referred to as cells. A cell can be provided by a base station, there being various different types of base stations. Different types of cells can provide different features. For example, cells can have different shapes, sizes and other characteristics.
A user can access the communication system by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE) or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. In wireless systems a communication device provides a transceiver station that can communicate with another communication device such as e.g. a base station of an access network and/or another user equipment. The communication device may access a carrier provided by a base station, and transmit and/or receive communications on the carrier.
Carrier aggregation (CA) can be used to increase performance. In carrier aggregation a plurality of component carriers on different frequencies are aggregated to increase bandwidth. In accordance with LTE Release 10 user equipment carrier aggregation (UE CA) capability integrates all carrier aggregation (CA) features in a capability set. In LTE release 10 UE CA capability has been comprehensively defined and includes features such as those related to UE radio frequency (RF) properties, decoding/encoding, hybrid automatic repeat request (HARQ) signalling support, blind decoding, the secondary serving cell (SCC) management, dual-Component Carrier capability, capability to monitor physical downlink control channel (PDCCH) on multiple cells, and so on. In other words, if a user equipment supports carrier aggregation (CA), it shall support all CA related features. Such a user equipment is necessarily a dual component carrier capable user equipment operable on multiple frequency resources. However, a user equipment that is capable only for communications on a single frequency carrier at a time cannot be configured to support the required dual component carrier aggregation related features and thus cannot provide any aggregation. On the other hand, single frequency communication devices may be desired in certain occasions, for example due to the lesser complexity and cost thereof.